WASHINGTON (AP) — Vice President Joe Biden has offered condolences to Ukrainian President Petro Poroshenko over killings in eastern Ukraine.

At last four people were killed by artillery fire in an overnight attack Saturday in Maryinka, a suburb of Donetsk where pro-Russia insurgents are holed up. The attack happened hours after Poroshenko vowed vengeance for the deaths of 19 troops in an insurgent rocket attack near the Russian border.

During their second conversation this week, the White House says Biden also expressed support for Poroshenko's efforts to convene a meeting with the separatists on a possible new cease-fire.

Biden also briefed Poroshenko on efforts by the U.S. and its allies to punish Russia if it continues to provide the insurgents with heavy weapons and equipment.